In exploring for and producing hydrocarbons from a subterranean formation, the measure of naturally occurring gamma radiation may be helpful. Natural gamma radiation is emitted by certain subsurface materials, such as, thorium (Th), uranium (U), and potassium (K). The radioisotopes or their equivalents of such substances are detected or measured. Typically natural gamma radiation detectors (or gamma ray detectors) are divided into two classes: gross counting and spectral. Spectral tools measure the gamma radiation over a spectrum and the gross counting tools focus on the total number of counts detected above a threshold.